We have a NGWF 321 with versión 5.9.1. After a power failure it doesn't seems to work until it's rebooted with the SMC active. It seems to be configured as it responds to somethings like VPN Mobile requests (it responds to the requests but doesn't authenticate users, even local users) but it didn't pass traffic througth any interface.

Is there anyway to get the firewall running without contact with the SMC after a reboot?

sounds like it loses configuration on reboot. This can happen if you did initial contact with a USB stick, and left that stick plugged in to the firewall. The next time it reboots it reads the USB stick again, tries to contact SMC and is left in initial config. If you have no USBs plugged in and the issue happens consistently, please open a ticket.

On a sidenote I would not recommend 5.9.1, go rather to 5.8.7 or 5.10.2 (or 5.10.3 when released soon). Note if you upgrade to 5.10 that SMC must then be already in 5.10 or 6.0.